As human society ever evolves into a more health conscious state and with the desire to become more efficient or to optimize the use of an individual's time, multitasking has become the metaphor for efficiency, wherein an individual performs a number of tasks simultaneously or in parallel to accomplish more tasks in a given amount of time as opposed to performing a number of tasks in a series manner that requires considerably more time. However, multitasking is not without its problems, as performing tasks simultaneously can require more versatility on the part of the individual and/or the related device or apparatus being used. As an example with a cell phone, the multitasking involves driving and making/receiving phone calls and phone conversation. The versatility required on the part of the individual is to safely split their attention between driving and making/receiving phone calls and phone conversation, in addition the cell phone must have more versatility than a home phone in being self contained and small in size neither of which are required in a home phone. Thus, along with the need or desire of an individual to manually move a carriage across a surface which can be for the purpose of moving the carriage from one location to another, or including a payload disposed on or in the carriage, such as items to carry in the using of a hand cart, a person(s) to carry in the using of a wheel chair, or a baby(s) or child to carry in the using of a stroller, while at the same time performing another task such as jogging or running for either physical fitness or to simply move the carriage from one location to another location in a more timely fashion resulting in the carriage being manually moved along a surface at a velocity varying from a slow walk to a fast run.
This results in examining the versatility required in the carriage, focusing specifically on the changing dynamics of turning/steering the carriage at varying velocities (speeds) across the surface in going from a slow walk to a fast run. As an introduction, one of the most significant problems is related to the current turning/steering ability in prior art jogging strollers is that it is highly burdensome to the individual using the jogging stroller by the constant lifting, adjusting, and/or lateral skidding of the fixed position front wheel (as prior art jogging strollers are without a steering mechanism, having typically three fixed wheels that rotate only and do not steer) for directional changes on jogging paths and the like, in fact when the current prior art jogging strollers are used on a concrete or asphalt surface, the skidding of the front wheel (to turn the prior art jogging stroller) is so difficult that many user's resort to pushing down on the jogging stroller handle thus suspending the single front wheel above the surface (to facilitate easy turning) with the jogging stroller only riding on its two rear wheels, resulting in awkward jogging stroller pushing across the surface by the user. Thus, the major issues are being in controlling the jogging stroller steering and smooth (vibration free) operation of the jogging stroller, when the jogging stroller is manually moved across the surface at varying speeds from a slow walk to a fast run.
The reason that the prior art jogging strollers shun the use of a conventional castor to steer or turn with (as in common on walking strollers) is that when the conventional castor is pushed across a surface (or a rough surface such as gravel) at higher than walking speed the conventional castor oscillates laterally (termed resonance) making the use of conventional castors on a jogging stroller untenable as the laterally oscillating castor wheel adds significant vibration to the stroller frame and results in turning the stroller being very difficult in being too quick or responsive. Perhaps, the most common analogy to draw upon is in the use of a conventional grocery shopping cart that is normally moved across a surface at a slow to moderate walking pace. Wherein, the grocery cart is steerable through a pair of front castors that have a fixed castor or fixed trail length, with the trail length being defined as the length or distance between the wheel contact point on the surface to the wheel vertical pivot axis, thus being where the vertical pivot axis theoretically intersects the surface, with the wheel vertical pivot axis adjacent to the grocery cart frame. With fixed trail length being defined as that the trail length does not change with the castor wheel pivoting through the vertical pivot axis and with the castor assembly being without any bias, urging, or dampening related to the wheel vertical pivot steering movement in positioning or controlling steering movement of the wheel. Also, a pair of grocery cart rear wheels that are affixed to the grocery cart frame in the sense that they are not steerable with the wheels only being rotatable about a fixed rotational axis. As most people are familiar, when moving the grocery cart along the surface at a slow to moderate walking pace the castor wheels steer adequately as the trail creates a rotational moment (being defined as an engineering moment in units of inch-pounds) to turn the wheel in the same direction as the individual turns the grocery cart and when the individual returns the grocery cart along the surface in a forward fashion (not turning) the wheel returns to being in a parallel position to the fixed wheels from the trail rotational moment (resulting in wheel pivoting movement along the vertical pivot axis) of the castor as the individual turns the grocery cart in an opposite direction. Both during the turning and non turning states of operation the grocery cart castor wheels operate substantially smoothly being without resonance, with resonance being defined as uncontrolled two way lateral movement or vibration parallel to the surface related to movement of the castor wheel about the vertical pivot axis.
However, as is well known to a number of grocery cart using individuals, when the grocery cart is manually moved across the surface at a higher velocity, i.e. when the individual is running, the front castor wheels go into resonance (sometimes called wheel shimmy or steering wobble) resulting in uncontrolled movement related to movement of the castor wheel about the vertical pivot axis with the wheel swinging side to side laterally, being parallel to the surface making the grocery cart difficult to move across the surface as the front castor wheel is virtually skidding sideways in its contact with the surface in an oscillating manner as opposed to the wheel properly rolling across the surface with minimal forward movement frictional resistance, i.e. making the grocery cart easy to push. The cause of this resonance of the castor wheel on the grocery cart when being moved across the surface at a velocity higher than a normal walking pace is that the pivotal (steering) instantaneous moment of the castor increases as a function of the velocity approximately squared, in addition the resonance can be excited by an undulation in the surface (surface unevenness, bumps, ruts, cracks, and the like) that the wheel comes in to rolling contact with. Thus, in taking the grocery cart from a velocity of about two (2) miles per hour (moderate walking pace) to about six (6) miles per hour (moderate jogging pace) the rotational moment of the castor increases about nine (9) times. Also, the frequency of the castor wheel resonance proportionally increases with the velocity of the grocery cart being in conjunction with the increase of the rotational moment. With the significant increase in the rotational moment of the castor there is a tendency for the wheel to overshoot in vertical pivot movement further causing a reactionary vertical pivot movement of the wheel from the rotational moment in the opposite direction. Further, in continuing the wheel overshoots in vertical pivot movement in the opposite direction causing a reactionary rotational moment and further continuing, thus resulting in lateral or horizontal resonance or uncontrolled movement of the castor wheel being highly undesirable as interfering with the smooth operation and steering ability of the grocery cart. However, this problem of castor resonance is not limited to grocery carts, as wheel chairs, hand carts, baby strollers, and the like typically are structurally very similar to grocery carts related to the castor wheels and affixed wheels as previously described. Note that this problem of castor resonance is not universal as long as the carriage is manually moved along the surface at a typical moderate walking velocity or slower as the castor resonance is rarely present due to the reduced rotational moment of the castor not causing the overshooting of the vertical pivot movement of the wheel that results in a reactionary and opposite rotational moment that ultimately leads to resonance of the castor wheel as previously described. However, if there is potential that the carriage will be manually moved across the surface at a velocity greater than the moderate walking pace then the aforementioned problem of castor resonance will most likely appear as in the case of jogging strollers and racing wheel chairs, being typical of manually operated carriages that are moved along a surface at a velocity higher than a moderate walking pace.
The problem of castor wheel resonance in carriages is recognized in the prior art for strollers particularly due to the advent of the “jogging stroller” and racing wheel chair wherein suddenly manually moving a carriage across a surface at a velocity substantially faster than moderate walking speed became an issue with the accompanying castor wheel resonance problems as previously described, that were not a problem with a traditional stroller or wheel chair that was typically manually moved along a surface at a moderate walking velocity. An example of a traditional “walking” stroller that is designed for moving along a surface at a moderate walking velocity utilizing castor wheels similar to the aforementioned grocery cart is found in U.S. Pat. No. 5,215,320 to Chen that discloses a walking stroller with the novel portion being the pivoting handlebar that automatically converts the front wheels into castor type wheel sets when pushing the stroller either forward or backward. Further, a typical example of a “walking” wheel chair is in U.S. Pat. No. 2,669,289 to Usher et al. that discloses a folding wheelchair that collapses width wise, with the novelty in the folding X type frame, having only standard type castor wheels. On the typical jogging stroller, due to the previously described castor resonance when the carriage is manually moved along a surface at a higher velocity being around running or jogging speed, the prior art jogging stroller overcomes the resonance issue simply by eliminating the castor and making the front wheel(s) affixed to the stroller frame with no castor or turning capabilities much the same as the rear wheels. Of course jogging strollers have other features such as longer extending handles to provide clearance for the jogger's feet and legs longer stride to minimize interference with the stroller frame and wheels and having larger diameter wheels that will rotate slower at higher velocities across the surface to reduce wheel imbalance vibration and give the stroller the capability roll upon more undulated or uneven surfaces at higher velocities with less chance of a sudden vertical force upon the stroller frame that could result in upsetting the stroller (causing the jogging stroller to potentially roll on its side) resulting from the wheel coming into contact with the uneven surface at a higher velocity from manually moving the stroller across the surface at jogging or running speed.
An example of a typical jogging stroller is given in U.S. Pat. No. 6,585,802 B2 to Sheehan, which discloses a jogging stroller as previously described being a conventional three fixed wheel design, wherein the novelty is in the ability to be a single seat or interchangeably a two seat design. Even though Sheehan is very representative of a typical jogging stroller, a number of design deficiencies become apparent in the jogging stroller arts, firstly, inherent rolling instability along an axis parallel to the direction of travel, as jogging strollers negotiate turns at higher velocity than walking strollers, roll over stability is important, however, ironically jogging strollers fare worse in this area than walking strollers by typically placing the child at a higher position above the surface increasing the composite roll over moment of the jogging stroller and child combined, due to larger diameter wheels and the stroller frame being higher above the surface (similar to a Sport Utility Vehicle [SUV] as compared to a passenger car), with the composite center of gravity of the child and the jogging stroller combined being vertically higher above the surface.
Secondly, addressing another typical jogging stroller design deficiency, as most jogging stroller designs have a single front wheel and two rear wheels as represented by Sheehan, further adds to roll over instability by reducing the effective “track” being the width of the wheel contacts upon the surface positioned transverse to the direction of travel of the stroller, depending upon the composite center of gravity for the child and the stroller combined as positioned between the front and rear wheel axles. As a way of partially overcoming the roll over instability as previously described, most jogging strollers place the composite center of gravity substantially adjacent to the rear wheel axle to allow the wider track of the rear wheels to have more influence on the effective track to regain some roll over stability. Also, as the typical jogging stroller has no wheel steering capability (castor or otherwise), as all the jogging stroller wheels are fixed to not allow steering having only wheel rotation, the only way the jogging stroller can be turned is by “skidding” or by lifting, or a combination thereof of the single fixed front wheel side to side or laterally transverse to the stroller direction of travel and in order to do this skidding easily the majority of weight should be removed from the front wheel with this being accomplished by two items. First, being the design center of gravity of the jogging stroller and child that is adjacent to the rear wheel axle and with the long jogging stroller handle giving the individual manually pushing the jogging stroller a longer moment arm to pivot the jogging stroller on the rear wheels thus making the contact of the front wheel to the surface very lightly loaded or even removing the front wheel contact with the surface temporarily. The method of currently steering present art jogging strollers is burdensome to the individual using the jogging stroller by the constant lifting, adjusting, and/or skidding the fixed position front wheel for directional changes on jogging paths and the like, especially in the case of a large child in the jogging stroller or with the use of twin (two) children jogging strollers.
Thirdly, addressing yet another typical jogging stroller design deficiency, again as most jogging stroller designs have a single front wheel and two rear wheels as represented by Sheehan, when maneuvering the jogging stroller up or down street curbs or steps, the single front wheel is placed either up or down as required by pivoting on the rear wheel axle the stroller frame being lifted or lowered via the extended length handle, wherein the single front wheel is placed on the curb or step (i.e. the new surface where the individual using the jogging stroller wants to go) and then using the handle the individual lifts the two rear wheels resulting in the entire jogging stroller weight resting upon the single front wheel. At this point a highly unstable situation exists, requiring the user to maintain a firm grip on the stroller handle, with all the weight and balance being on a single front wheel (similar to a unicycle) especially along the roll axis that is parallel to the jogging stroller direction of travel wherein the entire jogging stroller could roll sideways very easily being only resisted by the individual holding the handle until the two rear wheels are safely placed back on the new surface making the jogging stroller more stable about the roll axis.
Thus, the stroller arts have evolved into two distinct groupings based upon their use, being the walking strollers and the jogging strollers as represented by Chen and Sheehan respectively as previously described. Wherein, walking strollers cannot be easily used as jogging strollers having small diameter castored wheels that would result in undesirable castor resonance and vertical stroller frame shock loads from surface irregularities that are encountered at higher velocities along the surface, that increase the potential for a roll axis upset thus risking that the walking stroller could end up on its side if used on undulated surfaces at velocities higher that a moderate walking pace. The result of this is to have potential discomfort, injury, or death to the occupant of the stroller and to damage the stroller itself, in addition also potential injury or death to the user manually pushing the stroller. However, as most walking strollers have four wheels (two equally tracking front wheels and two equally tracking rear wheels), walking strollers are more stable along the roll axis during turns and are more stable when maneuvering the walking stroller up or down street curbs or steps, as the two front wheels are placed either up or down as required by pivoting on the rear wheels with the stroller frame being lifted or lowered via the handle, wherein the two front wheels are placed on the curb or step (i.e. the new surface where the individual using the walking stroller wants to go) and then using the handle the individual lifts the two rear wheels resulting in the entire jogging stroller weight resting upon the two front wheels, thus not having any compromise in roll axis stability than exists with all four wheels resting upon the surface. Conversely, if a jogging stroller is used as a walking stroller the lack of any steerable wheels is very inconvenient, requiring the individual using the jogging stroller to frequently lift or drag the single front wheel to move the front wheel sideways or transverse to the stroller direction of travel. Also, the jogging stroller has the previously described design deficiencies of turning or roll axis instability (however less critical at walking speed across the surface) and curb/step negotiating instability from the three wheel design. In addition, note that the three wheel All Terrain Vehicle (ATV) in no longer manufactured due to safety issues related to roll axis instability while turning resulting in rider injury or death, wherein the ATV design has been replaced using four wheels for enhanced roll axis stability.
There has been some recognition in the prior art as to the dichotomy in the stroller arts in looking at U.S. Pat. No. 6,779,804 B1 to Liu that discloses a jogging stroller that has a control block that can lock and unlock the front wheel from swivel (castor) movement. Liu recognizes the problem of steering a jogging stroller with a fixed front wheel, and claims to solve this problem by selectively allowing the front wheel to swivel for turning and then relocking the front wheel from swivel movement while going straight ahead with the stroller. Liu does not teach specifics related to rake, trail, pivot angles, on the front swivel wheel, as the Liu front swivel wheel is a design similar to the aforementioned grocery cart. Wherein, if the Liu front swivel wheel were unlocked (allowing swivel movement) when being used as a jogging stroller the front wheel would not only have resonance (defined as uncontrolled vacillating swivel movement of the wheel) but would also have excessively quick steering that would make control of the stroller difficult. It could be stated that Liu has a “hybrid” stroller that can lock the front swivel wheel for jogging mode and unlock the swivel wheel to turn in walking mode. However, as Liu has the conventional three wheel jogging stroller design the aforementioned turning instability and curb/step instability issues remain with Liu not improving upon the current separate functions of strollers that are designed for either walking or jogging. Some additional recognition of this dichotomy is shown in U.S. Pat. No. 6,449,801 B1 to Durrin that discloses add on front wheel castors for a jogging stroller, the add on castors are standard type castors, with the novel feature being only the attachment structure of the add on castors to the jogging stroller, which of course converts the jogging stroller to a walking stroller. Also, similarly in U.S. Pat. No. 6,443,467 B1 to Black disclosed is a functionally similar arrangement to Durrin, however, except that the jogging stroller is originally manufactured with interchangeable front wheels, with the walking stroller front wheels being of standard castor design and the jogging front wheel being of standard fixed design. Wherein, Black further recognizes the problem of castor front wheels on jogging strollers, reference Black's FIGS. 2 and 3.
What is needed is a stroller that substantially overcomes the aforementioned dichotomy in the stroller arts to allow a single stroller to function with substantial success as both a walking stroller and a jogging stroller without the need for structural hardware change outs between a jogging mode of use and a walking mode of use. This would include having several enhancements to overcome the identified deficiencies with the current jogging stroller arts related to having slower more controlled steering capabilities for a jogging stroller, enhanced roll axis stabilities, higher stability when negotiating curbs and steps with a jogging stroller, and retaining the current stroller arts capabilities of walking strollers that include steering, roll axis stability, and curb/step negotiating roll axis stability. In particular, enhancing the jogging stroller steering capability related to overcoming castor wheel resonance at higher velocities that accompany jogging velocities or speeds of the jogging stroller across the surface. Additionally, having enhanced roll axis stability while turning the stroller at speeds above walking, improved curb/step negotiating stability, and having the capability to have smooth and stable turning and non turning modes at speeds from walking to running.